1. Field of the Invention
The present invention relates to an antenna using an exterior metal frame and an electronic device utilizing the antenna.
2. Description of the Related Art
Electronic devices that have a communication function have recently become smaller in size and lighter in weight, and there is a demand for a capability to receive mobile communication services of different frequency bands using only one electronic device.
For example, an electronic device capable of simultaneously using multi-band signals is optionally required to provide mobile communication services using various frequency bands such as a Code Division Multiple Access (CDMA) service in 824˜894 MHz bands commercialized in Korea, a CDMA service in 1750˜1870 MHz bands, a CDMA service in 832˜925 MHz bands commercialized in Japan, a Personal Communications Service (PCS) service in 1850˜1990 MHz bands commercialized in the U.S.A, a Global System for Mobile communications (GSM) service in 880˜960 MHz bands commercialized in Europe, China, etc., a Digital Cellular System (DCS) service in 1710˜4880 MHz bands commercialized in some regions of Europe. In order to accommodate such multiple bands, a multi-band antenna having broadband characteristics is required.
However, according to research results in which a bandwidth is decreased in proportion to a decrease in a size of a multi-band antenna, a request for decreasing a size of a multi-band antenna and a request for providing broadband characteristics have a trade-off relation, and various attempts have been made to overcome such problem.
Meanwhile, a typical antenna used in a portable electronic device having a communication function include a Planar Inverted F Antenna (PIFA) or a monopole antenna as a basic structure, and a volume and the number of antennas to be mounted may be determined according to a service frequency and a bandwidth type. For example, a low frequency band of 700 MHz˜900 MHz and a high frequency band of 1700 MHz˜2100 MHz are used as a communication band.
For the monopole antenna, it is easy to obtain the broadband characteristics depending on a structure, but a matching characteristic deteriorates if an interval becomes closer to a ground in order to decrease an antenna size. In addition, for the PIFA, although it is easy to improve the matching characteristic by using a ground pin, as a result, it is difficult to obtain the broadband characteristics.
Accordingly, in order to overcome such a limitation while maintaining a basic monopole and PIFA shape, patterns with various shapes have been attempted, and various methods have been applied such as a method of decreasing a size by using a chip antenna, a matching method using a lumped element, and the like.
However, when a multi-band antenna is implemented that is smaller in size and has a broadband operation, a radiation efficiency characteristic generally deteriorates.
In addition, the multi-band antenna must satisfy various wireless communication services such as Long Term Evolution (LTE), Bluetooth® (BT), Global Positioning System (GPS), and Wireless Fidelity (WIFI). The multi-band antenna must satisfy the above-described communication band in a given antenna volume in a given electronic device, must have an electric field less than or equal to a Specific Absorption Rate (SAR) reference value for determining harmfulness to human body, and must overcome radiation performance interference caused by a metal enclosure, such as a metal frame or a Universal Serial Bus (USB).
An example for overcoming this includes a Metal Device Antenna (MDA) which utilizes a metal enclosure as a radiator, a bezel-antenna which utilizes a metal housing as a radiator, and the like.
In a current design trend, an electronic device uses an exterior metal frame structure, and there is a growing demand on such electronic device. However, applying a metal frame construction to an exterior case of the electronic device results in a growing problem of antenna radiation performance deterioration. In order to overcome this problem, a metal structure is avoided or the antenna is designed to be spaced apart from the metal structure. However, due to insufficient space for the antenna in the metal frame construction, it is difficult to overcome the performance problem.
In addition, with the advance of a communication technology, the electronic device must support additional operational frequency bands, and the space available to position the antenna is insufficient due when using the metal frame construction. Further, in view of current trends of designing the electronic device to be lighter, thinner, and simpler, antenna radiation performance may deteriorate due to the insufficient space available for the antenna.
In the electronic device using the exterior metal frame structure, it is difficult to ensure radiation performance due to a metal structure. Although the metal structure is avoided or an antenna is spaced apart in a design process in order to overcome this problem, since a space for the antenna is insufficient due to the metal frame construction, it is difficult to overcome the performance problem.
In addition, when the antenna is designed to avoid the metal frame structure, the electronic device using the exterior metal frame construction also has a structure in which the metal frame construction is utilized as a radiator due to a limitation of radiation performance improvement. However, the metal frame structure results in a difficulty to produce a multi-band resonance due to an insufficient space for the antenna and a constraint condition of a metal frame which can be utilized as the antenna.
In addition, it is difficult to overcome a human body influence caused when the metal frame is used as the radiator in the electronic device using the exterior metal frame structure.